If you want an opinion: I use both on my 8700g, no reason to not have them both loaded, costs nothing and very little memory space taken up. For following directions to a specific address, I think I like BB Maps a little better because of the little arrow which continues to point toward my final location.

Google maps for me. I don't have GPS, so don't need BB maps. Google maps has better graphics and when you zoom in the detail is better. The traffic feature is the one I use most. Find business is great too. BB maps is nice to find something in my address book though.